U.S. Pat. Nos. 3,934,430 of Fuso, 4,566,421 of Bauer et al., 3,603,112 of Sola, 5,417,187 of Meyer et al. 5,447,126 of Kondoh et al. disclose various fuel injection pump timing systems that include intermediate couplings between a cam shaft and a drive shaft. These intermediate couplings are axially adjustable by means of a drive source taken off of the engine. For example, Fuso discloses a hydraulic fluid pressure source (16), powered by the engine oil pump, that applies metered pressure to an inlet (22) of an hydraulic actuator of a injection timing control device (10). The present invention is an improvement upon the design concepts disclosed by these and other patents, wherein the power source for controlling the relative angular position of a camshaft to a drive shaft is dependent upon the crankshaft or another operative part of the engine.
Another currently used timing system for fuel injection pumps include a mechanical, centrifugally driven device, which varies a cam on an auxiliary drive to the fuel injection pump to adjust the relative cam angle about seven degrees of crankshaft rotation. In such a system, the relative cam angle is directly proportional to the revolutions per minute of the engine. The present invention provides a more sophisticated method of controlling the fuel pump angle that is continuously variable over a greater range of degrees and regardless of the engine RPM.